Rory McIlroy deliberately "wiped clean" up to eight mobile phone and electronic devices, the High Court has heard.

It was claimed that the handsets were cleared - even though they may have contained important information relating to his legal action against his former sports management company.

The factory resetting of devices, which it is claimed was also done to devices of three other key figures in the case - including Mr McIlroy's father Gerry - was "incredible for a person in his position", senior counsel Paul Sreenan said.

Mr Sreenan was opening an application brought by Dublin-based Horizon Sports Management, and two other companies, seeking orders from the court for further disclosure of documents and inspection of the devices of Mr McIroy and others.

Mr Sreenan said his clients had to bring the application because Mr McIroy had refused or failed to respond to requests for better disclosure and had asserted that teh player and three others close to him had also wiped their devices before passing them on to others or to charity.

Mr McIlroy is suing Horizon, along with Gurteen Ltd, with a registered address in Malta, and Canovan Management Services, also based in Dublin, claiming a representation agreement signed by him in December 2011 is invalid and unenforceable on a number of grounds.

The defendants deny the claims and have counter-claimed for some US $3m allegedly outstanding under the agreement for off-course revenues.

Mr Sreenan said today the amount of lost commission to his clients is now estimated at US$9m.

Mr McIroy says Horizon charged commission "many times greater" than is standard in the sports agency industry, including one agreement in which he must pay 20% of his sponsorship and 15% if the contract is renewed after 2017.

He also alleges Horizon is not entitled to be paid certain fees into the future related to his US$20m a year sponsorship deal with sportswear giant Nike.

Rory MclLroy tees off (Image: Andy Commins / Daily Mirror)

He says he has paid more than US$6.8m to Horizon based on commission rates of some 5% on his pre-tax on-course earnings and 20% for off-course.

This agreement was entered into when he was 22, with little business expertise and without the benefit of legal advice, he says.

Today, Mr Sreenan, for the defendants, said in order to defend the case and prove their counter-claim, the application for further and better discovery had been brought.

Mr McIlroy had given no satisfactory explanation for the destruction of electronic data on his devices, counsel said.

Mr Sreenan said if his side's experts gets the devices, it may be possible to recover some of the information sought or other information of assistance to the case.

It was a very serious matter for the administration of justice where someone involved in court proceedings had failed to preserve material, he said.

Mr McIlroy had initially claimed he changed his devices regularly because of his "transient lifesatyle".

And only today he had stated he changed them to avoid phone calls from journalists, counsel said.

The defendants believe he could not have changed phones and devices without backing up data and conversations because it would mean, for instance, ongoing conversations about who would be on the Ryder Cup team, would be wiped.

Earlier, Mr Sreenan said difficulties over the December 2011 agreement arose "when the ink was barely dry", counsel said.

Mr McIlroy had set his own company called "Rory McIlroy Inc", essentially to manage himself which was resisted by Horizon.

Around the same time, key figures who had worked for Horizon, including Mr McIroy's personal assistant and a consultant, started working for the golfer's new firm, counsel said.